As the Arctic settles into polar night, scientists are noticing that something has gone horribly wrong. Sea ice levels at the North Pole are at a record low—but even more startlingly, air temperatures are 36° F (20° C) higher than normal across the region.

At the same time, north-central Asia is experiencing equally abnormal temperatures, but in the opposite direction. There’s a cold spell looming over Siberia.

This map shows temperature departures from average. Areas in bright red and bright purple indicate temperature aberrations of up to 36° higher or lower (respectively) than normal.

Scientists are saying that this unusual warmth is due to a combination of two factors: record-low sea ice and moist air being pushed up from lower latitudes by the jet stream. The jet stream travels west to east across the North Hemisphere. Back in 2012, climatologist Jennifer Francis told NOVA that “we’re moving toward an increased tendency for the jet stream to get into these big wavy patterns that tend to move more slowly…So the weather that’s associated with them on the surface—either the storms or the high pressure areas, whatever it is—are going to stick around longer at a given location.”

That leads to increased frequency of extreme weather, but also to erratic migration of warm air toward the Arctic pole. It’s a self-fulfilling cycle: the movement of warm air toward the pole is caused by changes in the jet stream, but warmer temperatures in the Arctic narrow the gap between temperatures above and below the jet stream—causing it to become even wavier.

Here are Chris Mooney and Jason Samenow, reporting for The Washington Post:

Mark Serreze, who heads the National Snow and Ice Data Center in Boulder, Colo., agrees that something odd is going on. Not only are air temperatures unusually warm, but water temperatures are as well. “There are some areas in the Arctic Ocean that are as much as 25 degrees Fahrenheit above average now,” Serreze said. “It’s pretty crazy.”

What’s happening, he explains, is sort of a “double whammy.” On the one hand, there is a “very warm underlying ocean” due to the lack of sea ice forming above it. But, at the same time, kinks in the jet stream have allowed warm air to flow northward and frigid Arctic air to descend over Siberia.

“The sea ice is at a record low right now, for this time of year, that’s one thing,” Serreze said. “And why it’s so low—again, there’s so much heat in the upper ocean in these ice-free areas, the ice just can’t form right now. The ocean’s just got to get rid of this heat somehow, and it’s having a hard time doing so.”

Currently, if the trend continues, many North Americans won’t be spared from the extreme weather. The eastern part of the continent will likely have to endure a very cold winter because the jet stream is allowing air to “leak” into places it normally isn’t.

The unseasonably warm temperatures in the Arctic mean that sea ice levels will likely drop even lower. It’s possible the heat wave up north will snap, reversing the trend, but for now, ice levels next year could be extraordinarily thin.